<div class="panel panel-default">
    <div class="panel-heading" ng-click="changeOpen()">
        <h4 class="panel-title">
            <a href="#">
                {{heading}}
            </a>
        </h4>
    </div>
    <div class="panel-collapse" ng-class="{collapse:!isOpen}">
        <div class="panel-body" ng-transclude>
        </div>
    </div>
</div>